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-rw-r--r--mm/memcontrol.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b0757660663f..eb9571815f0c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1134,6 +1134,13 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
}
pc->mem_cgroup = mem;
+ /*
+ * We access a page_cgroup asynchronously without lock_page_cgroup().
+ * Especially when a page_cgroup is taken from a page, pc->mem_cgroup
+ * is accessed after testing USED bit. To make pc->mem_cgroup visible
+ * before USED bit, we need memory barrier here.
+ * See mem_cgroup_add_lru_list(), etc.
+ */
smp_wmb();
switch (ctype) {
case MEM_CGROUP_CHARGE_TYPE_CACHE: